/* eslint-disable no-unused-vars */
'use strict'

var root = window

// default options
var DEFAULTS = {
  // placement of the popper
  placement: 'bottom',

  gpuAcceleration: true,

  // shift popper from its origin by the given amount of pixels (can be negative)
  offset: 0,

  // the element which will act as boundary of the popper
  boundariesElement: 'viewport',

  // amount of pixel used to define a minimum distance between the boundaries and the popper
  boundariesPadding: 5,

  // popper will try to prevent overflow following this order,
  // by default, then, it could overflow on the left and on top of the boundariesElement
  preventOverflowOrder: ['left', 'right', 'top', 'bottom'],

  // the behavior used by flip to change the placement of the popper
  flipBehavior: 'flip',

  arrowElement: '[x-arrow]',

  arrowOffset: 0,

  // list of functions used to modify the offsets before they are applied to the popper
  modifiers: [
    'shift',
    'offset',
    'preventOverflow',
    'keepTogether',
    'arrow',
    'flip',
    'applyStyle'
  ],

  modifiersIgnored: [],

  forceAbsolute: false
}

/**
 * Create a new Popper.js instance
 * @constructor Popper
 * @param {HTMLElement} reference - The reference element used to position the popper
 * @param {HTMLElement|Object} popper
 *      The HTML element used as popper, or a configuration used to generate the popper.
 * @param {String} [popper.tagName='div'] The tag name of the generated popper.
 * @param {Array} [popper.classNames=['popper']] Array of classes to apply to the generated popper.
 * @param {Array} [popper.attributes] Array of attributes to apply, specify `attr:value` to assign a value to it.
 * @param {HTMLElement|String} [popper.parent=window.document.body] The parent element, given as HTMLElement or as query string.
 * @param {String} [popper.content=''] The content of the popper, it can be text, html, or node; if it is not text, set `contentType` to `html` or `node`.
 * @param {String} [popper.contentType='text'] If `html`, the `content` will be parsed as HTML. If `node`, it will be appended as-is.
 * @param {String} [popper.arrowTagName='div'] Same as `popper.tagName` but for the arrow element.
 * @param {Array} [popper.arrowClassNames='popper__arrow'] Same as `popper.classNames` but for the arrow element.
 * @param {String} [popper.arrowAttributes=['x-arrow']] Same as `popper.attributes` but for the arrow element.
 * @param {Object} options
 * @param {String} [options.placement=bottom]
 *      Placement of the popper accepted values: `top(-start, -end), right(-start, -end), bottom(-start, -right),
 *      left(-start, -end)`
 *
 * @param {HTMLElement|String} [options.arrowElement='[x-arrow]']
 *      The DOM Node used as arrow for the popper, or a CSS selector used to get the DOM node. It must be child of
 *      its parent Popper. Popper.js will apply to the given element the style required to align the arrow with its
 *      reference element.
 *      By default, it will look for a child node of the popper with the `x-arrow` attribute.
 *
 * @param {Boolean} [options.gpuAcceleration=true]
 *      When this property is set to true, the popper position will be applied using CSS3 translate3d, allowing the
 *      browser to use the GPU to accelerate the rendering.
 *      If set to false, the popper will be placed using `top` and `left` properties, not using the GPU.
 *
 * @param {Number} [options.offset=0]
 *      Amount of pixels the popper will be shifted (can be negative).
 *
 * @param {String|Element} [options.boundariesElement='viewport']
 *      The element which will define the boundaries of the popper position, the popper will never be placed outside
 *      of the defined boundaries (except if `keepTogether` is enabled)
 *
 * @param {Number} [options.boundariesPadding=5]
 *      Additional padding for the boundaries
 *
 * @param {Array} [options.preventOverflowOrder=['left', 'right', 'top', 'bottom']]
 *      Order used when Popper.js tries to avoid overflows from the boundaries, they will be checked in order,
 *      this means that the last ones will never overflow
 *
 * @param {String|Array} [options.flipBehavior='flip']
 *      The behavior used by the `flip` modifier to change the placement of the popper when the latter is trying to
 *      overlap its reference element. Defining `flip` as value, the placement will be flipped on
 *      its axis (`right - left`, `top - bottom`).
 *      You can even pass an array of placements (eg: `['right', 'left', 'top']` ) to manually specify
 *      how alter the placement when a flip is needed. (eg. in the above example, it would first flip from right to left,
 *      then, if even in its new placement, the popper is overlapping its reference element, it will be moved to top)
 *
 * @param {Array} [options.modifiers=[ 'shift', 'offset', 'preventOverflow', 'keepTogether', 'arrow', 'flip', 'applyStyle']]
 *      List of functions used to modify the data before they are applied to the popper, add your custom functions
 *      to this array to edit the offsets and placement.
 *      The function should reflect the @params and @returns of preventOverflow
 *
 * @param {Array} [options.modifiersIgnored=[]]
 *      Put here any built-in modifier name you want to exclude from the modifiers list
 *      The function should reflect the @params and @returns of preventOverflow
 *
 * @param {Boolean} [options.removeOnDestroy=false]
 *      Set to true if you want to automatically remove the popper when you call the `destroy` method.
 */
export default function Popper(reference, popper, options) {
  this._reference = reference.jquery ? reference[0] : reference
  this.state = {}

  // if the popper variable is a configuration object, parse it to generate an HTMLElement
  // generate a default popper if is not defined
  var isNotDefined = typeof popper === 'undefined' || popper === null
  var isConfig =
    popper && Object.prototype.toString.call(popper) === '[object Object]'
  if (isNotDefined || isConfig) {
    this._popper = this.parse(isConfig ? popper : {})
  }
  // otherwise, use the given HTMLElement as popper
  else {
    this._popper = popper.jquery ? popper[0] : popper
  }

  // with {} we create a new object with the options inside it
  this._options = Object.assign({}, DEFAULTS, options)

  // refactoring modifiers' list
  this._options.modifiers = this._options.modifiers.map(
    function (modifier) {
      // remove ignored modifiers
      if (this._options.modifiersIgnored.indexOf(modifier) !== -1) return

      // set the x-placement attribute before everything else because it could be used to add margins to the popper
      // margins needs to be calculated to get the correct popper offsets
      if (modifier === 'applyStyle') {
        this._popper.setAttribute('x-placement', this._options.placement)
      }

      // return predefined modifier identified by string or keep the custom one
      return this.modifiers[modifier] || modifier
    }.bind(this)
  )

  // make sure to apply the popper position before any computation
  this.state.position = this._getPosition(this._popper, this._reference)
  setStyle(this._popper, { position: this.state.position, top: 0 })

  // fire the first update to position the popper in the right place
  this.update()

  // setup event listeners, they will take care of update the position in specific situations
  this._setupEventListeners()
  return this
}

//
// Methods
//
/**
 * Destroy the popper
 * @method
 * @memberof Popper
 */
Popper.prototype.destroy = function () {
  this._popper.removeAttribute('x-placement')
  this._popper.style.left = ''
  this._popper.style.position = ''
  this._popper.style.top = ''
  this._popper.style[getSupportedPropertyName('transform')] = ''
  this._removeEventListeners()

  // remove the popper if user explicity asked for the deletion on destroy
  if (this._options.removeOnDestroy) {
    this._popper.remove()
  }
  return this
}

/**
 * Updates the position of the popper, computing the new offsets and applying the new style
 * @method
 * @memberof Popper
 */
Popper.prototype.update = function () {
  var data = { instance: this, styles: {} }

  // store placement inside the data object, modifiers will be able to edit `placement` if needed
  // and refer to _originalPlacement to know the original value
  data.placement = this._options.placement
  data._originalPlacement = this._options.placement

  // compute the popper and reference offsets and put them inside data.offsets
  data.offsets = this._getOffsets(this._popper, this._reference, data.placement)

  // get boundaries
  data.boundaries = this._getBoundaries(
    data,
    this._options.boundariesPadding,
    this._options.boundariesElement
  )

  data = this.runModifiers(data, this._options.modifiers)

  if (typeof this.state.updateCallback === 'function') {
    this.state.updateCallback(data)
  }
}

/**
 * If a function is passed, it will be executed after the initialization of popper with as first argument the Popper instance.
 * @method
 * @memberof Popper
 * @param {Function} callback
 */
Popper.prototype.onCreate = function (callback) {
  // the createCallbacks return as first argument the popper instance
  callback(this)
  return this
}

/**
 * If a function is passed, it will be executed after each update of popper with as first argument the set of coordinates and informations
 * used to style popper and its arrow.
 * NOTE: it doesn't get fired on the first call of the `Popper.update()` method inside the `Popper` constructor!
 * @method
 * @memberof Popper
 * @param {Function} callback
 */
Popper.prototype.onUpdate = function (callback) {
  this.state.updateCallback = callback
  return this
}

/**
 * Helper used to generate poppers from a configuration file
 * @method
 * @memberof Popper
 * @param config {Object} configuration
 * @returns {HTMLElement} popper
 */
Popper.prototype.parse = function (config) {
  var defaultConfig = {
    tagName: 'div',
    classNames: ['popper'],
    attributes: [],
    parent: root.document.body,
    content: '',
    contentType: 'text',
    arrowTagName: 'div',
    arrowClassNames: ['popper__arrow'],
    arrowAttributes: ['x-arrow']
  }
  config = Object.assign({}, defaultConfig, config)

  var d = root.document

  var popper = d.createElement(config.tagName)
  addClassNames(popper, config.classNames)
  addAttributes(popper, config.attributes)
  if (config.contentType === 'node') {
    popper.appendChild(
      config.content.jquery ? config.content[0] : config.content
    )
  } else if (config.contentType === 'html') {
    popper.innerHTML = config.content
  } else {
    popper.textContent = config.content
  }

  if (config.arrowTagName) {
    var arrow = d.createElement(config.arrowTagName)
    addClassNames(arrow, config.arrowClassNames)
    addAttributes(arrow, config.arrowAttributes)
    popper.appendChild(arrow)
  }

  var parent = config.parent.jquery ? config.parent[0] : config.parent

  // if the given parent is a string, use it to match an element
  // if more than one element is matched, the first one will be used as parent
  // if no elements are matched, the script will throw an error
  if (typeof parent === 'string') {
    parent = d.querySelectorAll(config.parent)
    if (parent.length > 1) {
      console.warn(
        'WARNING: the given `parent` query(' +
          config.parent +
          ') matched more than one element, the first one will be used'
      )
    }
    if (parent.length === 0) {
      throw "ERROR: the given `parent` doesn't exists!"
    }
    parent = parent[0]
  }
  // if the given parent is a DOM nodes list or an array of nodes with more than one element,
  // the first one will be used as parent
  if (parent.length > 1 && parent instanceof Element === false) {
    console.warn(
      'WARNING: you have passed as parent a list of elements, the first one will be used'
    )
    parent = parent[0]
  }

  // append the generated popper to its parent
  parent.appendChild(popper)

  return popper

  /**
   * Adds class names to the given element
   * @function
   * @ignore
   * @param {HTMLElement} target
   * @param {Array} classes
   */
  function addClassNames(element, classNames) {
    classNames.forEach(function (className) {
      element.classList.add(className)
    })
  }

  /**
   * Adds attributes to the given element
   * @function
   * @ignore
   * @param {HTMLElement} target
   * @param {Array} attributes
   * @example
   * addAttributes(element, [ 'data-info:foobar' ]);
   */
  function addAttributes(element, attributes) {
    attributes.forEach(function (attribute) {
      element.setAttribute(
        attribute.split(':')[0],
        attribute.split(':')[1] || ''
      )
    })
  }
}

/**
 * Helper used to get the position which will be applied to the popper
 * @method
 * @memberof Popper
 * @param config {HTMLElement} popper element
 * @param reference {HTMLElement} reference element
 * @returns {String} position
 */
Popper.prototype._getPosition = function (popper, reference) {
  var container = getOffsetParent(reference)

  if (this._options.forceAbsolute) {
    return 'absolute'
  }

  // Decide if the popper will be fixed
  // If the reference element is inside a fixed context, the popper will be fixed as well to allow them to scroll together
  var isParentFixed = isFixed(reference, container)
  return isParentFixed ? 'fixed' : 'absolute'
}

/**
 * Get offsets to the popper
 * @method
 * @memberof Popper
 * @access private
 * @param {Element} popper - the popper element
 * @param {Element} reference - the reference element (the popper will be relative to this)
 * @returns {Object} An object containing the offsets which will be applied to the popper
 */
Popper.prototype._getOffsets = function (popper, reference, placement) {
  placement = placement.split('-')[0]
  var popperOffsets = {}

  popperOffsets.position = this.state.position
  var isParentFixed = popperOffsets.position === 'fixed'

  //
  // Get reference element position
  //
  var referenceOffsets = getOffsetRectRelativeToCustomParent(
    reference,
    getOffsetParent(popper),
    isParentFixed
  )

  //
  // Get popper sizes
  //
  var popperRect = getOuterSizes(popper)

  //
  // Compute offsets of popper
  //

  // depending by the popper placement we have to compute its offsets slightly differently
  if (['right', 'left'].indexOf(placement) !== -1) {
    popperOffsets.top =
      referenceOffsets.top + referenceOffsets.height / 2 - popperRect.height / 2
    if (placement === 'left') {
      popperOffsets.left = referenceOffsets.left - popperRect.width
    } else {
      popperOffsets.left = referenceOffsets.right
    }
  } else {
    popperOffsets.left =
      referenceOffsets.left + referenceOffsets.width / 2 - popperRect.width / 2
    if (placement === 'top') {
      popperOffsets.top = referenceOffsets.top - popperRect.height
    } else {
      popperOffsets.top = referenceOffsets.bottom
    }
  }

  // Add width and height to our offsets object
  popperOffsets.width = popperRect.width
  popperOffsets.height = popperRect.height

  return {
    popper: popperOffsets,
    reference: referenceOffsets
  }
}

/**
 * Setup needed event listeners used to update the popper position
 * @method
 * @memberof Popper
 * @access private
 */
Popper.prototype._setupEventListeners = function () {
  // NOTE: 1 DOM access here
  this.state.updateBound = this.update.bind(this)
  root.addEventListener('resize', this.state.updateBound)
  // if the boundariesElement is window we don't need to listen for the scroll event
  if (this._options.boundariesElement !== 'window') {
    var target = getScrollParent(this._reference)
    // here it could be both `body` or `documentElement` thanks to Firefox, we then check both
    if (
      target === root.document.body ||
      target === root.document.documentElement
    ) {
      target = root
    }
    target.addEventListener('scroll', this.state.updateBound)
    this.state.scrollTarget = target
  }
}

/**
 * Remove event listeners used to update the popper position
 * @method
 * @memberof Popper
 * @access private
 */
Popper.prototype._removeEventListeners = function () {
  // NOTE: 1 DOM access here
  root.removeEventListener('resize', this.state.updateBound)
  if (this._options.boundariesElement !== 'window' && this.state.scrollTarget) {
    this.state.scrollTarget.removeEventListener(
      'scroll',
      this.state.updateBound
    )
    this.state.scrollTarget = null
  }
  this.state.updateBound = null
}

/**
 * Computed the boundaries limits and return them
 * @method
 * @memberof Popper
 * @access private
 * @param {Object} data - Object containing the property "offsets" generated by `_getOffsets`
 * @param {Number} padding - Boundaries padding
 * @param {Element} boundariesElement - Element used to define the boundaries
 * @returns {Object} Coordinates of the boundaries
 */
Popper.prototype._getBoundaries = function (data, padding, boundariesElement) {
  // NOTE: 1 DOM access here
  var boundaries = {}
  var width, height
  if (boundariesElement === 'window') {
    var body = root.document.body,
      html = root.document.documentElement

    height = Math.max(
      body.scrollHeight,
      body.offsetHeight,
      html.clientHeight,
      html.scrollHeight,
      html.offsetHeight
    )
    width = Math.max(
      body.scrollWidth,
      body.offsetWidth,
      html.clientWidth,
      html.scrollWidth,
      html.offsetWidth
    )

    boundaries = {
      top: 0,
      right: width,
      bottom: height,
      left: 0
    }
  } else if (boundariesElement === 'viewport') {
    var offsetParent = getOffsetParent(this._popper)
    var scrollParent = getScrollParent(this._popper)
    var offsetParentRect = getOffsetRect(offsetParent)

    // Thanks the fucking native API, `document.body.scrollTop` & `document.documentElement.scrollTop`
    var getScrollTopValue = function (element) {
      return element == document.body
        ? Math.max(document.documentElement.scrollTop, document.body.scrollTop)
        : element.scrollTop
    }
    var getScrollLeftValue = function (element) {
      return element == document.body
        ? Math.max(
            document.documentElement.scrollLeft,
            document.body.scrollLeft
          )
        : element.scrollLeft
    }

    // if the popper is fixed we don't have to substract scrolling from the boundaries
    var scrollTop =
      data.offsets.popper.position === 'fixed'
        ? 0
        : getScrollTopValue(scrollParent)
    var scrollLeft =
      data.offsets.popper.position === 'fixed'
        ? 0
        : getScrollLeftValue(scrollParent)

    boundaries = {
      top: 0 - (offsetParentRect.top - scrollTop),
      right:
        root.document.documentElement.clientWidth -
        (offsetParentRect.left - scrollLeft),
      bottom:
        root.document.documentElement.clientHeight -
        (offsetParentRect.top - scrollTop),
      left: 0 - (offsetParentRect.left - scrollLeft)
    }
  } else {
    if (getOffsetParent(this._popper) === boundariesElement) {
      boundaries = {
        top: 0,
        left: 0,
        right: boundariesElement.clientWidth,
        bottom: boundariesElement.clientHeight
      }
    } else {
      boundaries = getOffsetRect(boundariesElement)
    }
  }
  boundaries.left += padding
  boundaries.right -= padding
  boundaries.top = boundaries.top + padding
  boundaries.bottom = boundaries.bottom - padding
  return boundaries
}

/**
 * Loop trough the list of modifiers and run them in order, each of them will then edit the data object
 * @method
 * @memberof Popper
 * @access public
 * @param {Object} data
 * @param {Array} modifiers
 * @param {Function} ends
 */
Popper.prototype.runModifiers = function (data, modifiers, ends) {
  var modifiersToRun = modifiers.slice()
  if (ends !== undefined) {
    modifiersToRun = this._options.modifiers.slice(
      0,
      getArrayKeyIndex(this._options.modifiers, ends)
    )
  }

  modifiersToRun.forEach(
    function (modifier) {
      if (isFunction(modifier)) {
        data = modifier.call(this, data)
      }
    }.bind(this)
  )

  return data
}

/**
 * Helper used to know if the given modifier depends from another one.
 * @method
 * @memberof Popper
 * @param {String} requesting - name of requesting modifier
 * @param {String} requested - name of requested modifier
 * @returns {Boolean}
 */
Popper.prototype.isModifierRequired = function (requesting, requested) {
  var index = getArrayKeyIndex(this._options.modifiers, requesting)
  return !!this._options.modifiers.slice(0, index).filter(function (modifier) {
    return modifier === requested
  }).length
}

//
// Modifiers
//

/**
 * Modifiers list
 * @namespace Popper.modifiers
 * @memberof Popper
 * @type {Object}
 */
Popper.prototype.modifiers = {}

/**
 * Apply the computed styles to the popper element
 * @method
 * @memberof Popper.modifiers
 * @argument {Object} data - The data object generated by `update` method
 * @returns {Object} The same data object
 */
Popper.prototype.modifiers.applyStyle = function (data) {
  // apply the final offsets to the popper
  // NOTE: 1 DOM access here
  var styles = {
    position: data.offsets.popper.position
  }

  // round top and left to avoid blurry text
  var left = Math.round(data.offsets.popper.left)
  var top = Math.round(data.offsets.popper.top)

  // if gpuAcceleration is set to true and transform is supported, we use `translate3d` to apply the position to the popper
  // we automatically use the supported prefixed version if needed
  var prefixedProperty
  if (
    this._options.gpuAcceleration &&
    (prefixedProperty = getSupportedPropertyName('transform'))
  ) {
    styles[prefixedProperty] = 'translate3d(' + left + 'px, ' + top + 'px, 0)'
    styles.top = 0
    styles.left = 0
  }
  // othwerise, we use the standard `left` and `top` properties
  else {
    styles.left = left
    styles.top = top
  }

  // any property present in `data.styles` will be applied to the popper,
  // in this way we can make the 3rd party modifiers add custom styles to it
  // Be aware, modifiers could override the properties defined in the previous
  // lines of this modifier!
  Object.assign(styles, data.styles)

  setStyle(this._popper, styles)

  // set an attribute which will be useful to style the tooltip (use it to properly position its arrow)
  // NOTE: 1 DOM access here
  this._popper.setAttribute('x-placement', data.placement)

  // if the arrow modifier is required and the arrow style has been computed, apply the arrow style
  if (
    this.isModifierRequired(this.modifiers.applyStyle, this.modifiers.arrow) &&
    data.offsets.arrow
  ) {
    setStyle(data.arrowElement, data.offsets.arrow)
  }

  return data
}

/**
 * Modifier used to shift the popper on the start or end of its reference element side
 * @method
 * @memberof Popper.modifiers
 * @argument {Object} data - The data object generated by `update` method
 * @returns {Object} The data object, properly modified
 */
Popper.prototype.modifiers.shift = function (data) {
  var placement = data.placement
  var basePlacement = placement.split('-')[0]
  var shiftVariation = placement.split('-')[1]

  // if shift shiftVariation is specified, run the modifier
  if (shiftVariation) {
    var reference = data.offsets.reference
    var popper = getPopperClientRect(data.offsets.popper)

    var shiftOffsets = {
      y: {
        start: { top: reference.top },
        end: { top: reference.top + reference.height - popper.height }
      },
      x: {
        start: { left: reference.left },
        end: { left: reference.left + reference.width - popper.width }
      }
    }

    var axis = ['bottom', 'top'].indexOf(basePlacement) !== -1 ? 'x' : 'y'

    data.offsets.popper = Object.assign(
      popper,
      shiftOffsets[axis][shiftVariation]
    )
  }

  return data
}

/**
 * Modifier used to make sure the popper does not overflows from it's boundaries
 * @method
 * @memberof Popper.modifiers
 * @argument {Object} data - The data object generated by `update` method
 * @returns {Object} The data object, properly modified
 */
Popper.prototype.modifiers.preventOverflow = function (data) {
  var order = this._options.preventOverflowOrder
  var popper = getPopperClientRect(data.offsets.popper)

  var check = {
    left: function () {
      var left = popper.left
      if (popper.left < data.boundaries.left) {
        left = Math.max(popper.left, data.boundaries.left)
      }
      return { left: left }
    },
    right: function () {
      var left = popper.left
      if (popper.right > data.boundaries.right) {
        left = Math.min(popper.left, data.boundaries.right - popper.width)
      }
      return { left: left }
    },
    top: function () {
      var top = popper.top
      if (popper.top < data.boundaries.top) {
        top = Math.max(popper.top, data.boundaries.top)
      }
      return { top: top }
    },
    bottom: function () {
      var top = popper.top
      if (popper.bottom > data.boundaries.bottom) {
        top = Math.min(popper.top, data.boundaries.bottom - popper.height)
      }
      return { top: top }
    }
  }

  order.forEach(function (direction) {
    data.offsets.popper = Object.assign(popper, check[direction]())
  })

  return data
}

/**
 * Modifier used to make sure the popper is always near its reference
 * @method
 * @memberof Popper.modifiers
 * @argument {Object} data - The data object generated by _update method
 * @returns {Object} The data object, properly modified
 */
Popper.prototype.modifiers.keepTogether = function (data) {
  var popper = getPopperClientRect(data.offsets.popper)
  var reference = data.offsets.reference
  var f = Math.floor

  if (popper.right < f(reference.left)) {
    data.offsets.popper.left = f(reference.left) - popper.width
  }
  if (popper.left > f(reference.right)) {
    data.offsets.popper.left = f(reference.right)
  }
  if (popper.bottom < f(reference.top)) {
    data.offsets.popper.top = f(reference.top) - popper.height
  }
  if (popper.top > f(reference.bottom)) {
    data.offsets.popper.top = f(reference.bottom)
  }

  return data
}

/**
 * Modifier used to flip the placement of the popper when the latter is starting overlapping its reference element.
 * Requires the `preventOverflow` modifier before it in order to work.
 * **NOTE:** This modifier will run all its previous modifiers everytime it tries to flip the popper!
 * @method
 * @memberof Popper.modifiers
 * @argument {Object} data - The data object generated by _update method
 * @returns {Object} The data object, properly modified
 */
Popper.prototype.modifiers.flip = function (data) {
  // check if preventOverflow is in the list of modifiers before the flip modifier.
  // otherwise flip would not work as expected.
  if (
    !this.isModifierRequired(
      this.modifiers.flip,
      this.modifiers.preventOverflow
    )
  ) {
    console.warn(
      'WARNING: preventOverflow modifier is required by flip modifier in order to work, be sure to include it before flip!'
    )
    return data
  }

  if (data.flipped && data.placement === data._originalPlacement) {
    // seems like flip is trying to loop, probably there's not enough space on any of the flippable sides
    return data
  }

  var placement = data.placement.split('-')[0]
  var placementOpposite = getOppositePlacement(placement)
  var variation = data.placement.split('-')[1] || ''

  var flipOrder = []
  if (this._options.flipBehavior === 'flip') {
    flipOrder = [placement, placementOpposite]
  } else {
    flipOrder = this._options.flipBehavior
  }

  flipOrder.forEach(
    function (step, index) {
      if (placement !== step || flipOrder.length === index + 1) {
        return
      }

      placement = data.placement.split('-')[0]
      placementOpposite = getOppositePlacement(placement)

      var popperOffsets = getPopperClientRect(data.offsets.popper)

      // this boolean is used to distinguish right and bottom from top and left
      // they need different computations to get flipped
      var a = ['right', 'bottom'].indexOf(placement) !== -1

      // using Math.floor because the reference offsets may contain decimals we are not going to consider here
      if (
        (a &&
          Math.floor(data.offsets.reference[placement]) >
            Math.floor(popperOffsets[placementOpposite])) ||
        (!a &&
          Math.floor(data.offsets.reference[placement]) <
            Math.floor(popperOffsets[placementOpposite]))
      ) {
        // we'll use this boolean to detect any flip loop
        data.flipped = true
        data.placement = flipOrder[index + 1]
        if (variation) {
          data.placement += '-' + variation
        }
        data.offsets.popper = this._getOffsets(
          this._popper,
          this._reference,
          data.placement
        ).popper

        data = this.runModifiers(data, this._options.modifiers, this._flip)
      }
    }.bind(this)
  )
  return data
}

/**
 * Modifier used to add an offset to the popper, useful if you more granularity positioning your popper.
 * The offsets will shift the popper on the side of its reference element.
 * @method
 * @memberof Popper.modifiers
 * @argument {Object} data - The data object generated by _update method
 * @returns {Object} The data object, properly modified
 */
Popper.prototype.modifiers.offset = function (data) {
  var offset = this._options.offset
  var popper = data.offsets.popper

  if (data.placement.indexOf('left') !== -1) {
    popper.top -= offset
  } else if (data.placement.indexOf('right') !== -1) {
    popper.top += offset
  } else if (data.placement.indexOf('top') !== -1) {
    popper.left -= offset
  } else if (data.placement.indexOf('bottom') !== -1) {
    popper.left += offset
  }
  return data
}

/**
 * Modifier used to move the arrows on the edge of the popper to make sure them are always between the popper and the reference element
 * It will use the CSS outer size of the arrow element to know how many pixels of conjuction are needed
 * @method
 * @memberof Popper.modifiers
 * @argument {Object} data - The data object generated by _update method
 * @returns {Object} The data object, properly modified
 */
Popper.prototype.modifiers.arrow = function (data) {
  var arrow = this._options.arrowElement
  var arrowOffset = this._options.arrowOffset

  // if the arrowElement is a string, suppose it's a CSS selector
  if (typeof arrow === 'string') {
    arrow = this._popper.querySelector(arrow)
  }

  // if arrow element is not found, don't run the modifier
  if (!arrow) {
    return data
  }

  // the arrow element must be child of its popper
  if (!this._popper.contains(arrow)) {
    console.warn('WARNING: `arrowElement` must be child of its popper element!')
    return data
  }

  // arrow depends on keepTogether in order to work
  if (
    !this.isModifierRequired(this.modifiers.arrow, this.modifiers.keepTogether)
  ) {
    console.warn(
      'WARNING: keepTogether modifier is required by arrow modifier in order to work, be sure to include it before arrow!'
    )
    return data
  }

  var arrowStyle = {}
  var placement = data.placement.split('-')[0]
  var popper = getPopperClientRect(data.offsets.popper)
  var reference = data.offsets.reference
  var isVertical = ['left', 'right'].indexOf(placement) !== -1

  var len = isVertical ? 'height' : 'width'
  var side = isVertical ? 'top' : 'left'
  var translate = isVertical ? 'translateY' : 'translateX'
  var altSide = isVertical ? 'left' : 'top'
  var opSide = isVertical ? 'bottom' : 'right'
  var arrowSize = getOuterSizes(arrow)[len]

  //
  // extends keepTogether behavior making sure the popper and its reference have enough pixels in conjuction
  //

  // top/left side
  if (reference[opSide] - arrowSize < popper[side]) {
    data.offsets.popper[side] -= popper[side] - (reference[opSide] - arrowSize)
  }
  // bottom/right side
  if (reference[side] + arrowSize > popper[opSide]) {
    data.offsets.popper[side] += reference[side] + arrowSize - popper[opSide]
  }

  // compute center of the popper
  var center =
    reference[side] + (arrowOffset || reference[len] / 2 - arrowSize / 2)

  var sideValue = center - popper[side]

  // prevent arrow from being placed not contiguously to its popper
  sideValue = Math.max(Math.min(popper[len] - arrowSize - 8, sideValue), 8)
  arrowStyle[side] = sideValue
  arrowStyle[altSide] = '' // make sure to remove any old style from the arrow

  data.offsets.arrow = arrowStyle
  data.arrowElement = arrow

  return data
}

//
// Helpers
//

/**
 * Get the outer sizes of the given element (offset size + margins)
 * @function
 * @ignore
 * @argument {Element} element
 * @returns {Object} object containing width and height properties
 */
function getOuterSizes(element) {
  // NOTE: 1 DOM access here
  var _display = element.style.display,
    _visibility = element.style.visibility
  element.style.display = 'block'
  element.style.visibility = 'hidden'
  var calcWidthToForceRepaint = element.offsetWidth

  // original method
  var styles = root.getComputedStyle(element)
  var x = parseFloat(styles.marginTop) + parseFloat(styles.marginBottom)
  var y = parseFloat(styles.marginLeft) + parseFloat(styles.marginRight)
  var result = {
    width: element.offsetWidth + y,
    height: element.offsetHeight + x
  }

  // reset element styles
  element.style.display = _display
  element.style.visibility = _visibility
  return result
}

/**
 * Get the opposite placement of the given one/
 * @function
 * @ignore
 * @argument {String} placement
 * @returns {String} flipped placement
 */
function getOppositePlacement(placement) {
  var hash = { left: 'right', right: 'left', bottom: 'top', top: 'bottom' }
  return placement.replace(/left|right|bottom|top/g, function (matched) {
    return hash[matched]
  })
}

/**
 * Given the popper offsets, generate an output similar to getBoundingClientRect
 * @function
 * @ignore
 * @argument {Object} popperOffsets
 * @returns {Object} ClientRect like output
 */
function getPopperClientRect(popperOffsets) {
  var offsets = Object.assign({}, popperOffsets)
  offsets.right = offsets.left + offsets.width
  offsets.bottom = offsets.top + offsets.height
  return offsets
}

/**
 * Given an array and the key to find, returns its index
 * @function
 * @ignore
 * @argument {Array} arr
 * @argument keyToFind
 * @returns index or null
 */
function getArrayKeyIndex(arr, keyToFind) {
  var i = 0,
    key
  for (key in arr) {
    if (arr[key] === keyToFind) {
      return i
    }
    i++
  }
  return null
}

/**
 * Get CSS computed property of the given element
 * @function
 * @ignore
 * @argument {Eement} element
 * @argument {String} property
 */
function getStyleComputedProperty(element, property) {
  // NOTE: 1 DOM access here
  var css = root.getComputedStyle(element, null)
  return css[property]
}

/**
 * Returns the offset parent of the given element
 * @function
 * @ignore
 * @argument {Element} element
 * @returns {Element} offset parent
 */
function getOffsetParent(element) {
  // NOTE: 1 DOM access here
  var offsetParent = element.offsetParent
  return offsetParent === root.document.body || !offsetParent
    ? root.document.documentElement
    : offsetParent
}

/**
 * Returns the scrolling parent of the given element
 * @function
 * @ignore
 * @argument {Element} element
 * @returns {Element} offset parent
 */
function getScrollParent(element) {
  var parent = element.parentNode

  if (!parent) {
    return element
  }

  if (parent === root.document) {
    // Firefox puts the scrollTOp value on `documentElement` instead of `body`, we then check which of them is
    // greater than 0 and return the proper element
    if (root.document.body.scrollTop || root.document.body.scrollLeft) {
      return root.document.body
    } else {
      return root.document.documentElement
    }
  }

  // Firefox want us to check `-x` and `-y` variations as well
  if (
    ['scroll', 'auto'].indexOf(getStyleComputedProperty(parent, 'overflow')) !==
      -1 ||
    ['scroll', 'auto'].indexOf(
      getStyleComputedProperty(parent, 'overflow-x')
    ) !== -1 ||
    ['scroll', 'auto'].indexOf(
      getStyleComputedProperty(parent, 'overflow-y')
    ) !== -1
  ) {
    // If the detected scrollParent is body, we perform an additional check on its parentNode
    // in this way we'll get body if the browser is Chrome-ish, or documentElement otherwise
    // fixes issue #65
    return parent
  }
  return getScrollParent(element.parentNode)
}

/**
 * Check if the given element is fixed or is inside a fixed parent
 * @function
 * @ignore
 * @argument {Element} element
 * @argument {Element} customContainer
 * @returns {Boolean} answer to "isFixed?"
 */
function isFixed(element) {
  if (element === root.document.body) {
    return false
  }
  if (getStyleComputedProperty(element, 'position') === 'fixed') {
    return true
  }
  return element.parentNode ? isFixed(element.parentNode) : element
}

/**
 * Set the style to the given popper
 * @function
 * @ignore
 * @argument {Element} element - Element to apply the style to
 * @argument {Object} styles - Object with a list of properties and values which will be applied to the element
 */
function setStyle(element, styles) {
  function is_numeric(n) {
    return n !== '' && !isNaN(parseFloat(n)) && isFinite(n)
  }
  Object.keys(styles).forEach(function (prop) {
    var unit = ''
    // add unit if the value is numeric and is one of the following
    if (
      ['width', 'height', 'top', 'right', 'bottom', 'left'].indexOf(prop) !==
        -1 &&
      is_numeric(styles[prop])
    ) {
      unit = 'px'
    }
    element.style[prop] = styles[prop] + unit
  })
}

/**
 * Check if the given variable is a function
 * @function
 * @ignore
 * @argument {*} functionToCheck - variable to check
 * @returns {Boolean} answer to: is a function?
 */
function isFunction(functionToCheck) {
  var getType = {}
  return (
    functionToCheck &&
    getType.toString.call(functionToCheck) === '[object Function]'
  )
}

/**
 * Get the position of the given element, relative to its offset parent
 * @function
 * @ignore
 * @param {Element} element
 * @return {Object} position - Coordinates of the element and its `scrollTop`
 */
function getOffsetRect(element) {
  var elementRect = {
    width: element.offsetWidth,
    height: element.offsetHeight,
    left: element.offsetLeft,
    top: element.offsetTop
  }

  elementRect.right = elementRect.left + elementRect.width
  elementRect.bottom = elementRect.top + elementRect.height

  // position
  return elementRect
}

/**
 * Get bounding client rect of given element
 * @function
 * @ignore
 * @param {HTMLElement} element
 * @return {Object} client rect
 */
function getBoundingClientRect(element) {
  var rect = element.getBoundingClientRect()

  // whether the IE version is lower than 11
  var isIE = navigator.userAgent.indexOf('MSIE') != -1

  // fix ie document bounding top always 0 bug
  var rectTop =
    isIE && element.tagName === 'HTML' ? -element.scrollTop : rect.top

  return {
    left: rect.left,
    top: rectTop,
    right: rect.right,
    bottom: rect.bottom,
    width: rect.right - rect.left,
    height: rect.bottom - rectTop
  }
}

/**
 * Given an element and one of its parents, return the offset
 * @function
 * @ignore
 * @param {HTMLElement} element
 * @param {HTMLElement} parent
 * @return {Object} rect
 */
function getOffsetRectRelativeToCustomParent(element, parent, fixed) {
  var elementRect = getBoundingClientRect(element)
  var parentRect = getBoundingClientRect(parent)

  if (fixed) {
    var scrollParent = getScrollParent(parent)
    parentRect.top += scrollParent.scrollTop
    parentRect.bottom += scrollParent.scrollTop
    parentRect.left += scrollParent.scrollLeft
    parentRect.right += scrollParent.scrollLeft
  }

  var rect = {
    top: elementRect.top - parentRect.top,
    left: elementRect.left - parentRect.left,
    bottom: elementRect.top - parentRect.top + elementRect.height,
    right: elementRect.left - parentRect.left + elementRect.width,
    width: elementRect.width,
    height: elementRect.height
  }
  return rect
}

/**
 * Get the prefixed supported property name
 * @function
 * @ignore
 * @argument {String} property (camelCase)
 * @returns {String} prefixed property (camelCase)
 */
function getSupportedPropertyName(property) {
  var prefixes = ['', 'ms', 'webkit', 'moz', 'o']

  for (var i = 0; i < prefixes.length; i++) {
    var toCheck = prefixes[i]
      ? prefixes[i] + property.charAt(0).toUpperCase() + property.slice(1)
      : property
    if (typeof root.document.body.style[toCheck] !== 'undefined') {
      return toCheck
    }
  }
  return null
}

/**
 * The Object.assign() method is used to copy the values of all enumerable own properties from one or more source
 * objects to a target object. It will return the target object.
 * This polyfill doesn't support symbol properties, since ES5 doesn't have symbols anyway
 * Source: https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Object/assign
 * @function
 * @ignore
 */
if (!Object.assign) {
  Object.defineProperty(Object, 'assign', {
    enumerable: false,
    configurable: true,
    writable: true,
    value: function (target) {
      if (target === undefined || target === null) {
        throw new TypeError('Cannot convert first argument to object')
      }

      var to = Object(target)
      for (var i = 1; i < arguments.length; i++) {
        var nextSource = arguments[i]
        if (nextSource === undefined || nextSource === null) {
          continue
        }
        nextSource = Object(nextSource)

        var keysArray = Object.keys(nextSource)
        for (
          var nextIndex = 0, len = keysArray.length;
          nextIndex < len;
          nextIndex++
        ) {
          var nextKey = keysArray[nextIndex]
          var desc = Object.getOwnPropertyDescriptor(nextSource, nextKey)
          if (desc !== undefined && desc.enumerable) {
            to[nextKey] = nextSource[nextKey]
          }
        }
      }
      return to
    }
  })
}
